Over the past several years a number of less invasive or minimally invasive surgical techniques have been developed. Examples of such techniques are various endoscopic or laparoscopic procedures, angioplasty procedures, atherectomy procedures, and the like. While the instruments and devices used in these minimally invasive procedures are complex and hence relatively expensive, the procedures are gaining more and more acceptance. It is believed the reasons for this acceptance are the reduced risk to the patient, as the patient often doesn't have to undergo general anesthesia or the time under general anesthesia is greatly reduced. Perhaps, more importantly, the recovery time required after a minimally invasive procedure is much less, thus greatly reducing hospital costs.
One of the more invasive procedures being performed today is open heart surgery. Such procedures require the use of general anesthesia, sternotomy, use of extracoporeal by-pass, recovery in an intensive care unit, and a stay of at least a few days in the hospital. Although such procedures carry a low mortality rate, they are quite expensive.
Currently in the United States approximately 100,000 defective heart valves are replaced annually, at an approximate cost of $30-50,000 per procedure, and thus it would be desirable if heart valves could be replaced using minimally invasive techniques. It would be especially advantageous if a defective heart valve could be removed via an endovascular procedure, that is, a procedure where the invasion into the body is through a blood vessel such as the femoral artery. The procedure is then carried out percutaneously and transluminally using the vascular system to convey appropriate devices to the position in the body wherein it is desired to carry out the desired procedure. An example of such a procedure would be angioplasty, wherein a catheter carrying a small balloon at its distal end is manipulated through the body's vessels to a point where there is a blockage in a vessel. The balloon is expanded to create an opening in the blockage, and then the balloon is deflated and the catheter and balloon are removed from the vessel.
Endovascular procedures have substantial benefits both from the standpoint of health and safety as well as cost. Such procedures require minimal invasion of the human body, and there is consequently considerable reduction and in some instances even elimination, of the use of a general anesthesia and much shorter hospital stays.
In the last few years a number of atherectomy devices have been developed. These are endovascular devices used to remove plaque and other abnormal deposits from vessels. Representative examples of such devices are those disclosed in U.S. Pat. Nos. 4,445,509, 4,646,736, and 4,990,134.
A number of minimally invasive techniques for replacing heart valves have been developed. Such techniques have been reported in an article by H. R. Andersen et al., entitled "Transluminal Implantation of Artificial Heart Valves", European Heart Journal (1992), Vol. 13, pp. 704-708; in an article by L. L. Knudsen et al., entitled "Catheter-Implanted Prosthetic Heart Valves", The International Journal of Artificial Organs, Vol. 16, No. 5 (1993), pp. 253-262; and in an article by D. Pavcnik et al., entitled "Development and Initial Experimental Evaluation of a Prosthetic Aortic Valve for Trans-Catheter Placement", Radiology (1992), Vol. 183, pp. 151-154. While the devices and techniques reported are clearly experimental, it appears that each of them suffers from one or more of the following problems: (1) secure placement of the heart valve; (2) durability of the heart valve; (3) ease of placement; (4) thrombogenicity, (5) leakage or regurgitation of blood, (6) excessive pressure gradient across the valve, and (7) size of the device and delivery system, as well as other similar problems. In addition, none of the above described devices or methods deals with the presence of a diseased or defective native valve.
An endovascular valve replacement procedure is described in Stevens, U.S. Pat. No. 5,370,685. While it cannot be discerned whether the procedure disclosed will work, it is evident that the replacement valve is structurally limited and will have the disadvantages associated with the problems discussed above.